Implantable stimulation devices deliver electrical stimuli to nerves and tissues for the therapy of various biological disorders, such as pacemakers to treat cardiac arrhythmia, defibrillators to treat cardiac fibrillation, cochlear stimulators to treat deafness, retinal stimulators to treat blindness, muscle stimulators to produce coordinated limb movement, spinal cord stimulators to treat chronic pain, cortical and deep brain stimulators (DBS) to treat motor and psychological disorders, and other neural stimulators to treat urinary incontinence, sleep apnea, shoulder subluxation, etc. The description that follows will generally focus on the use of the invention within a spinal cord stimulation (SCS) system, such as that disclosed in U.S. Pat. No. 6,516,227. However, the present invention may find applicability with any implantable medical device (IMD) or in any IMD system.
As shown in FIG. 1, a SCS system includes an Implantable Pulse Generator (IPG) 10 (hereinafter, and more generically, IMD 10), which includes a biocompatible device case 12 formed of titanium for example. The case 12 typically holds the circuitry and battery 14 (FIG. 3) necessary for the IMD 10 to function. The IMD 10 is coupled to electrodes 16 via one or more electrode leads 18 (two of which are shown). The proximal ends of the leads 18 are coupled to the IMD 10 at one or more lead connectors 20 fixed in a header 22, which can comprise an epoxy for example. There are sixteen electrodes (E1-E16) in the illustrated example, although the number of leads and electrodes is application specific and therefore can vary. In an SCS application, two electrode leads 18 are typically implanted on the right and left side of the dura within the patient's spinal column. The proximal ends of the leads 18 are then tunneled through the patient's tissue 35 (FIG. 3) to a distant location, such as the buttocks, where the IMD case 12 is implanted, at which point they are coupled to the lead connectors 20.
An IMD 10 is typically supported by and communicates with one or more external devices, and FIGS. 2A and 2B provide examples of such devices. FIG. 2A depicts an external controller 40 for the IMD 10. The external controller 40 is used to establish a bi-directional wireless data link 45 with the IMD 10, as explained further with respect to FIG. 3. The external controller 40 is typically used to send or adjust the therapy settings the IMD 10 will provide to the patient. If the IMD 10 is an IPG 10 as depicted in FIG. 1, such therapy settings may include which electrodes 16 are active to issue therapeutic current pulses; whether such electrodes sink or source current (i.e., electrode polarity); the duration, frequency, and amplitude of the pulses, etc., which settings together comprise a stimulation program for the IMD 10. External controller 40 can also act as a receiver of data from the IMD 10, such as various data reporting on the IMD's status and the level of the IMD's battery 14.
As shown in FIG. 2A, external controller 40 is typically configured in a hand-held, portable housing 42, and powered by an internal battery (52; FIG. 3), which battery may be a primary battery or rechargeable. The external controller 40 includes a graphical user interface (GUI) similar to that used for a cell phone, including buttons 44 and a screen 46, and may have other interface aspects as well, such as a speaker. While an external controller 40 is typically a device custom built by the manufacturer of the IMD 10 and dedicated in its functionality to IMD communications, external controller 40 may also comprise general purpose, freely programmable mobile device having suitable wireless communication functionality, such as a smart cell phone. In this case, a Medical Device Application (MDA) can be executed on the mobile device to configure it for use as an IMD external controller, and to allow for control and monitoring of the IMD 10. See, e.g., U.S. Pat. No. 9,186,518, which is incorporated herein by reference in its entirety.
FIG. 2B depicts an external charger 60 for the IMD 10, which is used to recharge the IMD 10's rechargeable battery 14 by producing an AC magnetic charging field 65 (FIG. 3). The user interface of the external charger may be simple compared to the external controller 40. For example, the external charger 60 may lack a screen. Instead, the external charger 60 may simply include an on/off button 62 for magnetic charging field 65 generation, and status light emitting diode (LED) 64. Although not shown, external charger 60 may also include a speaker useful to indicate alignment between the external charger and the IMD 10, as is well known. See, e.g., U.S. Patent Application Publication 2013/0096651. External charger 60 is also typically hand-held and portable, and integrated within a housing 62.
Internal structures of the external controller 40, the external charger 60, and the IMD 10 are shown in cross section in FIG. 3, which also depicts the bi-directional data link 45 between the external controller 40 and the IMD 10, and the magnetic charging field 65 produced by the external controller 60.
IMD 10 as shown in FIG. 3 includes the battery 14 mentioned earlier. Although an IMD 10 can include a primary (non-rechargeable) battery, battery 14 in this example is rechargeable. Recharging of the battery 14 is assisted by a charging coil 24. The magnetic charging field 65 from the external charger 60 induces a current in this charging coil 24, which current is then rectified to DC levels and used to charge the battery 14.
The magnetic charging field 65 is produced by a charging coil 66 in the external charger 60. Power for the production of the magnetic charging field 65 is provided by a battery 68 in the external charger 60, which may be primary or rechargeable. The coil 66 is typically electrically coupled to one or more circuit boards 70, 72 in the external charger 60, as is other circuitry 74 (control circuitry such as a microcontroller; coil driver circuitry, etc.). In the configuration shown in FIG. 3, circuitry 74 is affixed to a vertical circuit board 72 to reduce the generation in the circuitry 74 of Eddy currents caused by the magnetic charging field 65. Such Eddy currents may generate heat unwanted heat, providing a patient safety risk, and will also generally detract from the efficiency of power transfer by sinking some of the energy in the magnetic charging field 65. The battery 68 is also moved outside of the charging coil 66 for the same reason, as its typically-metallic case can also heat and sink magnetic charging field 65 energy. Magnetic charging field 65 may comprises a field of 80 kHz for example, and may not be modulated with data. However, Load Shift Keying (LSK) may be used to transmit data back to the external charger 60 during production of the magnetic charging field 65, as is well known. See, e.g., the '651 Publication.
Because charging the battery 14 in the IMD 10 may take some time, it is desired to hold the external charger 60 in close proximity to and in alignment with the IMD 10 during a charging session when the magnetic charging field 65 is produced. Typically, and as disclosed in U.S. Publication 2014/0025140, this occurs using an external charger holding device 80, such as a belt 82, as shown in FIG. 4. The belt 82 fastens around the patient's waist, and can be secured by a fastening device 84, such as a buckle, clasp, snaps, Velcro, etc. The belt 82 can be adjustable to fit patients with different waist sizes. The belt 82 includes a pouch 86, which is generally located on the belt 82 in a position where the IMD 10 is implanted in the patient, such as the back of the patient proximate to the buttocks. A slot 88 or other opening in the belt 82 allows the external charger 60 to be inserted into the pouch 86, such that the external changer 60 is, like the pouch 86, generally aligned with the IMD 10. Once placed in the pouch 86, the patient can press the on/off switch 64 (FIG. 3) on the external charger 60 to begin a charging session—i.e., to produce magnetic charging field 65—or the user can turn the charger on before inserting it in the pouch 86. Affixing the external charger 60 to the patient using belt 82 allows the patient to move or walk while using the external charger 60, and thus can charge his implant “on the go.” See also U.S. Publication 2012/0012630, describing another belt for an external charger.
Data communications between the IMD 10 and the external controller 40 (FIG. 2A) along link 45 is assisted by a telemetry antenna 28 in the IMD 10, as shown in FIG. 3. Telemetry antenna 28 can take different forms depending on the physics of the link 45. If magnetic induction is used with link 45 comprising an AC magnetic field, the antenna can comprise a coil antenna 28a. In this case, the antenna 50 provided in the external controller 40 may likewise comprise a coil antenna 50a. If short-range but far-field electromagnetic RF telemetry is used for link 45, the antenna in the IMD 10 can comprise an RF antenna 28b, such as a wire, slot, or patch antenna, as shown in dotted lines. In this case, the telemetry antenna 50 provided in the external controller 40 may likewise comprise an RF antenna 50b, as explained further in the above-incorporated '518 Patent.
Telemetry antenna 28 in the IMD 10 and telemetry antenna 50 in the external controller 40 preferably act to both transmit and receive data. As such, antennas 28 and 50 are respectively coupled to circuitries 26 and 56 to modulate transmitted data and demodulate received data according to a data scheme employed on link 45. For example, if coil antennas 28a and 50a are respectively employed in the IMD 10 and external controller 40, Frequency Shift Keying (FSK) can be used to modulate transmitted data on the link 45. As one skilled in the art understands, this scheme transmits a serial string of data bits, with individual bits being defined by a frequency shift with respect to a nominal center frequency. If the center frequency for data on link 45 comprises 125 kHz for example, a ‘0’ bit may be represented as a transmission at 121 kHz, while a ‘1’ may be represented as a transmission at 129 kHz. Although not shown, one or more orthogonal coil antennas 50a driven or received out of phase could be used in external controller 40 as well to improve communication coupling with the IMD 10 along link 45, as discussed in U.S. Publication 2009/0069869, with which the reader is assumed familiar. If RF antennas 28b and 50b are respectively employed in the IMD 10 and external controller 40, short-range RF schemes may be used on link 45, such as Bluetooth, WiFi, or the Medical Implant Communication Service (MICS), as explained further in the above-incorporated '518 Patent. These are merely examples of telemetry schemes useable on link 45, and other means of communication could be used as well.
One skilled in the art will understand that circuitries 26 and 56 can additionally include other circuits needed for IMD 10 and external controller 40 functionality, and may include control circuits such as a microcontroller. Circuitry 26 in the IMD 10 may additionally include stimulation circuitry for forming the therapeutic current pulses defined by the stimulation program at the electrodes 16 (when IMD 10 comprises an IPG). Electrical components in the IMD 10 and external controller 40 are respectively coupled to circuit boards 30 and 54 as shown.
Transmission of data (link 45) or power (link 65) occurs transcutaneously, i.e., through the patient's tissue 35, which is particularly useful in an implantable medical device system.
Although the external controller 40 and external charger 60 are depicted separately to this point, the art has recognized that the functionality of both of these devices can be integrated into a single device or system. One example disclosed in U.S. Pat. No. 8,335,569 depicts a combined integrated external controller/charger having a single housing, which housing includes the antennas (coils) necessary for both IMD data telemetry and IMD battery charging functions.
Another example of an integrated external controller/charger system 90 is depicted in FIGS. 5A and 5B, as disclosed in U.S. Pat. No. 8,498,716, which is incorporated herein by reference in its entirety. As shown in FIG. 5A, system 90 includes an integrated external controller/charger 100 that can be similar in construction and function to the external controller 40 (FIG. 2A). Thus, the integrated external controller/charger 100 again includes a hand-held, portable housing 42 and a GUI including buttons 44 and a screen 46. Housing 42 may also again contain one or more antennas 50a or 50b for communicating with the IMD 10 via a link 45 (FIG. 3), to transmit therapy settings or to receive IMD status information for example.
However, unlike the external controller 40 of FIG. 2A, the integrated external controller/charger 100 additionally contains circuitry to drive an external charging coil assembly 110, which is attachable via a cable 112 and connector 114 to a port 48 (e.g., a USB port) on the housing 42. The external charging coil assembly 110 includes a charging coil 116 similar in function to the coil 66 used in the external charger 60 (FIGS. 2B, 3). Charging coil 116 may be mounted to a substrate 118 in the assembly 110, which may comprise a circuit board, and may include contact points for ends of the charging coil 116 and for the termination 120 of the signals in cable 112. Substrate 118 may be flexible, such as made of polyimide or Kapton for example, or rigid like a traditional printed circuit board. The external charging coil assembly 100 may include a housing 122 for the coil 116 and substrate 118, which may comprise an overmolded material such as silicone or hard plastic for example. As shown, a hole 124 may be present in the housing 122 of the assembly 110 in the center of the charging coil 116. Although not shown, the external charging coil assembly 110 may additionally contain one or more temperature sensing devices, such as thermistors or thermocouples, to measure the temperature of the assembly 110 and to report such temperature to the external controller/charger 100 so that production of the magnetic charging field 65 can be controlled accordingly (e.g., so as to not exceed a safe temperature set point).
The external controller/charger 100 is additionally programmed to allow a user to charge the IMD battery 14 via the external charging coil assembly 110 using the GUI of the device 100, with appropriate user selection at the GUI causing magnetic charging field 65 to be produced, as shown in FIG. 5B.
The implementation of the integrated external controller/charger system 90 is touted in the '716 Patent as beneficial, as it achieves good integration of the charging and data telemetry. Because the external charging coil assembly 110 does not contain substantial electronics, such as its own display, battery, microcontroller, etc., it is less bulky and easier to carry in conjunction with the external controller/charger 100. Moreover, the external charging coil assembly 110 lacks its own user interface, and instead the GUI of the external controller/charger 100 is used to control and monitor IMD charging functionality. This makes system 90 easy to use, as the patient does not need to learn how to use or manipulate two completely independent devices—i.e., an external controller 40 (FIG. 2A) and an external charger 60 (FIG. 2B). The '716 Patent further notes that because the external controller/charger 100 powers both itself and the external charging coil assembly 110 via the battery 52 internal to its housing 42 (FIG. 3), there is only one battery to replace and/or recharge in the system 90.